Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates generally to voting solenoid-operated valve devices for testing and controlling industrial process systems, and more particularly to a variable function voting solenoid-operated valve apparatus that provides low-cost, high-reliability testing and control of a fluid media processing or manufacturing plant.
2. Background of the Invention
Modern process or manufacturing plants consist of innumerable individual components. These components are integrated to form operational systems controlled by instrumentation and control systems consisting of a variety of sensors and controllers. The operational and control systems serve not only to achieve desired process conditions and parameters, but also to allow a plant facility to safely modify or discontinue operation of all or a portion of the plant""s systems and components in order to avoid predetermined deleterious activities and conditions.
For example, safety systems or configurations require routine testing and maintenance in order to verify their continued proper performance with respect to the plant functions for which they were intended. From both an operational and economic vantage, it is highly desirable that such safety systems or configurations should not unnecessarily modify or discontinue operation of the plant systems or components being monitored. One manner in which such safety systems or configurations function is by the isolation or venting of certain process fluids when an unsafe operating condition has been detected by the safety system or configuration. Depending on a particular processing or manufacturing plant""s intended operational parameters, this isolation and/or venting of process fluids can be accomplished by actuating process valves. When these process valves are pneumatically actuated spring return type valves, either applying pressure or venting pressure to the valve actuator will move the valve to the open or closed position. One of the means by which pneumatic supply is controlled to the process valves is through the use of one or more solenoid-operated valves.
In function, the solenoid-operated valves of such safety systems or configurations serve to initiate a process whereby a fluid or pneumatic supply is either applied to or vented from the process valve actuator when one or more operatively associated solenoid-operated valves changes state or position in a predetermined manner, e.g., when the solenoid-operated valve is de-energized by the logic control system. The plant processing system and any subservient system or component controlled thereby is then placed in an operational configuration pre-designated as a xe2x80x9csafety actionxe2x80x9d.
It is frequently the case that testing and maintenance of an individual solenoid valve should be accomplished without initiating the safety action, thereby avoiding an undesired modification or discontinuance of the plant process system being monitored. However, most prior solenoid valve configurations have necessarily required a trade-off by operators between either discontinuing safety monitoring during testing and maintenance or risking false initiations of the safety action as a result of limited or incomplete testing and maintenance.
For example, a xe2x80x9c1 out of 1xe2x80x9d solenoid-operated valve configuration is well-known in the art wherein a single solenoid-operated valve is employed for activating the system""s safety action by actuating process valves upon detection of an unsafe condition. Such configurations can achieve high plant safety availability when solenoid-operated valve operation is regularly tested by de-energizing the solenoid-operated valve and then monitoring a venting of the fluid or pneumatic supply through an exhaust body such as an anodized aluminum or composite material manifold or the like. Since the process valve and ultimately the plant process system (or its constituent components) may be affected by such venting, testing of the solenoid-operated valve can only be performed under plant bypass conditions, wherein the fluid or pneumatic supply is allowed to pass directly to the process valve or its constituent components by means of a bypass valve. When the solenoid-operated valve is bypassed for testing, the safety action (actuation of the process valve) intended to avoid the unsafe condition cannot be initiated by the solenoid-operated valve.
In practice, the overall safety availability performance of a 1 out of 1 solenoid-operated valve is therefore limited by the percentage of operational time required in a bypass state for testing and maintenance. Moreover, such configurations can achieve only relatively low plant system reliability outside of testing and routine maintenance, since an unexpected component failure within the solenoid-operated valve, for example, a coil failure, will necessarily cause an inadvertent venting or isolation of the fluid or pneumatic supply, i.e., actuation of the process valve and initiation of the safety action.
A xe2x80x9c1 out of 2xe2x80x9d solenoid-operated valve configuration is also known wherein correct functioning of only one of a pair of solenoid-operated valves connected in operative association is required to actuate the process valve and initiate the safety action. Since only one of the solenoid-operated valves is required to actuate the process valve, relatively high plant safety availability is inherently provided.
Moreover, such a configuration does not require the high testing frequency of the 1 out of 1 solenoid-operated valve system; however, routine testing and maintenance of the device are still required for ordinary safety applications. Similar to the 1 out of 1 solenoid valve, the 1 out of 2 configuration typically requires bypassing the system""s safety action during testing. Accordingly, the device is incapable of actuating te process valve, and of isolating or venting the process fluid supply in response to an unsafe condition while the system is in bypass mode. Thus, the safety availability performance of the 1 out of 2 solenoid is also limited by the percentage of operational time required for bypassing and testing. Moreover, since there are two discrete solenoids capable of initiating the safety action, a failure in a single solenoid-operated valve coil can lead to the inadvertent actuation of the process valve and isolation or venting of the process fluid.
A xe2x80x9c2 out of 2xe2x80x9d configuration has also been employed wherein both solenoid-operated valves must correctly function to actuate the process valve and initiate the safety action. Since both solenoid-operated valves must function properly, high plant system reliability is readily obtained. However, since the likelihood of individual component failure within the solenoid-operated valve system is effectively doubled (for example, both solenoid-operated valves must always function properly), the configuration suffers from relatively low safety availability unless function-tested very frequently. Also, initiation of the safety action is again prevented during testing and maintenance because the plant system must be bypassed for such functions, wherein the fluid or pneumatic supply is allowed to pass directly to the process valve or its constituent components by means of a bypass valve. When the solenoid-operated valves are bypassed for testing, the safety action, actuation of the process valve, intended to avoid the unsafe condition cannot be initiated by the solenoid-operated valves. The testing and maintenance cycle is generally time and manpower intensive since most of the known 2 out of 2 configurations are still tested manually. As with the previously discussed solenoid-operated valve systems, therefore, the safety availability performance of the device is limited by the percentage of operational time required during bypassing and testing or maintenance.
A more sophisticated approach has involved a xe2x80x9c2 out of 3xe2x80x9d voting solenoid-operated valve system wherein two out of three solenoid-operated valves must operate properly to actuate the process valve and isolate or vent the process fluid. The configuration achieves high safety availability since only two of the three solenoid-operated valves must function to initiate a safety action, and high plant system reliability since two of the three solenoid-operated valves must experience a coil failure or the like for an inadvertent actuation of the process valve and isolation or venting of the process fluid supply to occur. The safety availability is also superior to the previously discussed solenoid systems insofar as the device can be tested or maintained without bypassing the safety action.
In practice, however, those of skill in the pertinent arts have found that the use of three solenoid-operated valves substantially increases the overall price of the system. Moreover, additional logic control system input and output points are required relative to simpler configurations, and thus installation and operating expenses are also increased. In short, the high costs associated with the 2 out of 3 solenoid configuration have virtually negated its effective industrial utility.
Finally, elaborate xe2x80x9cquad-votingxe2x80x9d configurations have also been attempted wherein both high safety availability and high plant system reliability are reportedly achieved. However, the use of four solenoid-operated valves in a voting configuration has been found to require an unusually large amount of space to accommodate its complex pneumatic tubing, and such complexity obviously increases the associated capital and installation costs. Perhaps even more importantly, many commercial operators of voting solenoid-operated valve systems have been found to particularly disfavor the complex quad-voting configuration because of the elevated potential for testing and maintenance error associated therewith.
3. Objects of the Invention
In view of the foregoing, an object of the present invention is to provide a variable function voting solenoid-operated valve apparatus having both a high safety availability and high plant system reliability that does not require a plant system to be bypassed during testing and maintenance. A further object of the invention is to provide a variable function voting solenoid-operated valve apparatus wherein actuation of the process valve and isolation or venting of the process fluid will occur only if both solenoid-operated valves in a system are actuated, and wherein either of the solenoid-operated valves can default to the safety action without inadvertently actuating the process valve and isolating or venting the process fluid. A still further object of the invention is to provide a variable function voting solenoid-operated valve apparatus wherein either a xe2x80x9c1 out of 1 with hot stand-byxe2x80x9d mode or a xe2x80x9c2 out of 2 with high diagnosticsxe2x80x9d mode may be selected by an operator using a known logic control system depending on the technical requirements of a given plant environment. A still further object of the invention is to provide a variable function voting solenoid-operated valve apparatus wherein a plurality of pressure sensing devices are incorporated to detect failure of either of a pair of operatively associated solenoid-operated valves so as to prevent inadvertent initiation of a safety action, and wherein a bypass valve is provided to allow on-line maintenance of the device should one of the solenoid-operated valves or pressure sensing devices fail during operation or when a failure is detected during a testing or maintenance cycle. A still further object of the invention is to provide a means to partially initiate the safety action, without undesired modification or disruption of the plant process system being monitored, providing diagnostic information on the safety action.
According to one aspect of the present invention, a variable function voting solenoid-operated valve apparatus useful for testing and controlling industrial process systems by actuating process valves is provided wherein the apparatus comprises a first solenoid-operated valve and a second solenoid-operated valve; a bypass valve; and a plurality of pressure sensing devices including a first pressure sensor in fluid communication with said first solenoid-operated valve, a second pressure sensor in fluid communication with said second solenoid-operated valve, and a third pressure sensor in fluid communication with said bypass valve.
In a presently preferred embodiment of the invention, a variable function voting solenoid-operated valve apparatus is provided comprising a first solenoid-operated valve and a second solenoid-operated valve, wherein actuation of the process valve and therefore the safety action is provided by means of a pneumatic supply to actuate the process valve being directed by the solenoid-operated valve apparatus, and electrical control of said first and second solenoid-operated valves is provided by means of a logic control system or processor; a bypass valve actuated by a key-switch; a valve manifold, wherein said first and second solenoid-operated valves and said bypass valve are joined by said valve manifold; and a plurality of pressure switches including a first pressure switch in fluid communication with said first solenoid-operated valve, a second pressure switch in fluid communication with said second solenoid-operated valve, and a third pressure switch in fluid communication with said key-switch actuated bypass valve. In a further embodiment of the invention, the present variable function voting solenoid apparatus is controlled by a logic control system or processor, wherein said logic control system selectively enables an operator to select between one of at least two discrete apparatus operational modes. In a still further embodiment of the invention, an operator of the apparatus may select from discrete operational modes including a 1 out of 1 with hot stand-by mode (hereinafter referred to as xe2x80x9c1oo1-HSxe2x80x9d) and a 2 out of 2 with high diagnostics mode (hereinafter referred to as xe2x80x9c2oo2-Dxe2x80x9d). In a further embodiment of the invention, the present variable function voting solenoid apparatus can be used in either operational mode (xe2x80x9c1oo 1-HSxe2x80x9d or xe2x80x9c2oo2-Dxe2x80x9d) to partially initiate the safety action to provide diagnostic information on the systems capability to achieve the safety action.